1. Field of the Invention
The present invention relates to an active vibration isolation support system that includes an elastic body that receives a load from a vibrating body, a liquid chamber having a wall of which at least a part is Conned from the elastic body, an actuator that moves a moveable core out and back by the actuator receiving a supply of current according to the vibrational state of the vibrating body, a movable member that is moved out and back by the movable core of the actuator so as to change the capacity of the liquid chamber, and a controller which controls the current that is supplied to the actuator.
2. Description of the Related Art
An active vibration isolation support system is known from Japanese Patent Application Laid-open No. 2003-113892.
This active vibration isolation support system calculates a crank angular velocity from a time interval between crank pulses output every time a crankshaft rotates through a predetermined angle, calculates a crankshaft torque from a crank angular acceleration obtained by differentiating the crank angular velocity with respect to time, estimates an engine vibrational state as a variation in the torque, and controls the supply of current to a coil of the actuator according to the engine vibrational state, thus exhibiting a vibration isolation function.
When the internal space of an actuator case housing the actuator is sealed in order to substantially prevent water or dust from entering the interior of the actuator case, the internal pressure changes accompanying the moving out and back of the movable member, which forms a part of a wall around the internal space, caused by the actuator. For example, by energizing the coil of the actuator so as to move the movable member toward the inside of the actuator case, the pressure of the internal space of the actuator case increases, and this increase in pressure might interfere with movement of the movable member. Therefore, even if the control means controls the current supplied to the coil of the actuator in order to generate a predetermined thrust for the movable member, the target thrust cannot be generated because of the variation in pressure of the internal space of the actuator case, so that the active vibration isolation support system might not be able to exhibit a desired performance.